In this project, we will investigate the quantum properties of nanoscale mechanical resonators. Suspended structures will be made of Al, SiN, GaAs, carbon nanotubes, and photonic crystals, covering frequencies in the MHz and GHz range. The vibrations will be excited by electrical means. To overcome the thermal noise, cooling of the low-frequency resonators will be performed. We will use two cooling techniques: sideband cooling due to the coupling to an electromagnetic resonator, and optical cooling. For the ultra-sensitive read-out of the displacement, optical methods will be used, as well as a novel technique based on incorporating the resonator into an arm of a superconducting interference device (SQUID). A part of the project will be devoted to developing methods of quantum manipulation with mechanical vibrations. Successful implementation of the project will require integration of mechanical and optical devices into nanoelectronic circuits. A close collaboration of theorists and experimentalists is essential for the success of the project. The theoretical research will concentrate on modeling cooling and read-out schemes by considering interaction of electrons with non-equilibrium phonons and photons. The project addresses basic research; mid-term and long-term applications are expected in the areas of sensing and quantum information.